The present invention relates to an improved method for manufacturing a fine-patterned thick film conductor structure and a method for manufacturing a printed circuit board using the same.
The fine-patterned thick film conductor structure has been required in the fields of small size coils, high package density connectors and high circuit density wirings in which high magnitude current is used. Coils have usually been manufactured by winding wires. In this method, however, it is difficult to manufacture the small size coils and the windings have variance. A so-called printed coil having an etched copper foil having a thickness of several tens microns cannot attain a fine pattern because of side etching which extends to the extent of double of the thickness. It can attain a pattern of 2 to 3 lines/mm at most. Accordingly, it is difficult to manufacture the small size coil by this method. (See, for example, U.S. Pat. No. 3,269,861.) In recent years, as the motors for cassette tape recorders and VTR's have been miniaturized, it has been desired to develop and put into practice a fine coil having a fine-patterned thick film conductor structure.
The inventors of the present invention have proposed, in the above-referenced copending U.S. application Ser. No. 219,155, a method for manufacturing a high density fine-patterned thick film conductor structure which is free from shortcircuit due to the thickening of the conductors, by thickening a thin film conductor pattern having a thickness of 0.1-10 .mu.m formed on an insulative substrate by electroplating conductor in the condition of a cathode current density of no less than 5 A/dm.sup.2. However, when the thin film conductor pattern is directly electoplated, the thickness of the plated layer is not uniform if the length of the fine-patterned conductor structure exceeds that corresponding to a resistance of 5 ohms. In another method in which an unpatterned thin film conductor structure formed on an insulative substrate is electroplated with a resist pattern mask being placed thereon, it is necessary to remove the resist and etch away narrow lines of the fine pattern. Thus, this method includes a number of steps and requires high accuracy of process.